Thank you everyone for the replies, debate, advice and suggestions

Rather than requote the whole post I'll just throw a few comments back.

First off, have PMed James@MSD my Evolution Chips serial no to see what spec and rev limit it was designed for.

R&B Plenum was mentioned by Mike Rainbird on the Escos forum as well, that's staying as I like it, but it was intended for a much bigger build long term. Not sure if I'll be going that route, but have had a couple people suggest it won't help, and a couple others saying it won't be the sole or main reason for my late boost.

Regarding revs, I've no idea

Rev counter didn't work when I bought the car I thought due to the only recently installed wasted spark. I simply joined the two green wires together that went to the old coil, and the rev counter worked straight away, then soon after the gearbox broke, and the car went off the road for a couple months while I sorted that and a new clutch. Anyway, now back on the road, rev counter dead. Checked the green wires and they're still joined so something else seems to have killed it.

Anyone got any suggestions where to start looking or what to test to see why it's dead?

I have a SECS monitor, but the screen is too small to look at while boosting down the road, so no idea what that's reading, but it does read 1/2 actual revs due to the wasted spark. Will see if I can get some mug to passenger with me next time I give the car some death.

Thanks again for all the input so far